ISOTOPE GEOCHEMISTRY OF COPPER AND ZINC IN THE GEOSPHERE AND BIOSPHERE
Bibliographic record
Abstract
Zinc homeostasis is disrupted during the formation of breast tumours. Malignant tumours contain elevated levels of Zn (mean = 14.93 ± 11.05 μg/g) and isotopically light d66Zn values (mean = -0.40 ± 0.15 ‰) compared to histologically normal tissue adjacent to malignant tumours (pvalue = 3.4 x 10-5 and pvalue = 0.04, respectively), indicating that the processes that govern Zn accumulation in malignant tumours are fundamentally different from those that control homeostasis in healthy cells and benign tumour cells. No statistically significant difference in bulk serum Zn concentration or d66Zn value was observed between healthy controls and patients. Serum zinc concentrations have been reported to fall by between about 10 and 25% three hours postprandial (i.e. after eating). I investigated whether this well-documented effect is accompanied by a zinc isotopic shift, with implications for study design and sampling protocols. No postprandial change in stable Zn isotope composition (mean Δ66Zn180-minute – Baseline = 0.01 ± 0.09‰, 2SD) was observed. I proposed that hemodilution and the rapid, efficient postprandial transfer of albumin-bound Zn from serum to the liver and pancreas is responsible for the lack of postprandial serum Zn isotopic response. These results indicate that studies examining solely the distribution of Zn isotopes in serum may obtain samples without considering timing of the most recent meal. However, future studies seeking to compare serum Zn concentrations with d66Zn values should draw blood samples in the morning after overnight fasting. With the goal of expanding the number and variety of geological and biological materials that can be precisely and accurately measured, I characterized the copper isotopic compositions of ten reference materials by multiple collector inductively coupled plasma mass spectrometry using a combined standard-sample bracketing and internal normalisation mass bias correction using agallium internal standard. The reference materials measured in this thesis possess complex and ii varied matrices with copper concentrations ranging from 1.2 μg g-1 to 497 μg g-1, and δ65Cu values ranging from -0.20‰ to 0.52‰ with an average expanded uncertainty of ± 0.07‰ (U, k = 2), covering much of the natural copper isotope variability observed in the environment.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".